“It’s a typewriter’s keyboard. Also a computer’s,” said Gamache. “Qwerty is the first few letters on the top line.”
“What the person using Qwerty generally does is go to the keyboard and type the letter next to the one you really mean. Very easy to decode. This isn’t it, by the way. No.” Jérôme hauled himself up and Gamache almost tumbled into the void left by his body. “I went through a whole lot of ciphers and frankly I haven’t found anything. I’m sorry.”
Gamache had been hopeful this master of codes would be able to crack the Hermit’s. But like so much else with this case, it wouldn’t reveal itself easily.
“But I think I know what sort of code it is. I think it’s a Caesar’s Shift.”
“Go on.”
“Bon,” said Jérôme, relishing the challenge and the audience. “Julius Caesar was a genius. He’s really the cipher fanatic’s emperor. Brilliant. He used the Greek alphabet to send secret messages to his troops in France. But later he refined his codes. He switched to the Roman alphabet, the one we use now, but he shifted the letters by three. So if the word you want to send is kill, the code in Caesar’s Shift becomes . . .” He grabbed a piece of paper and wrote the alphabet.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Then he circled four letters.
NLOO
“See?”
Gamache and Thérèse leaned over his messy desk.
“So he just shifted the letters,” said Gamache. “If the code under the carvings is a Caesar’s Shift, can’t you just decode it that way? Move the letters back by three?”
He looked at the letters under the sailing ship.
“That would make this . . . L, T, P. Okay, I don’t have to go further. It makes no sense.”
“No, Caesar was smart and I think this Hermit was too. Or at least, he knew his codes. The brilliance of the Caesar’s Shift is that it’s almost impossible to break because the shift can be whatever length you want. Or, better still, you can use a key word. One you and your contact aren’t likely to forget. You write it at the beginning of the alphabet, then start the cipher. Let’s say it’s Montreal.”
He went back to his alphabet and wrote Montreal under the first eight letters, then filled in the rest of the twenty-six beginning with A.
A B C D E F G H I J K L M N O P Q R S T U V W X Y S